Jennie the German shepherd-heeler mix had always been an agile dog. So when Maribeth Ashley, the owner of the 6-year-old rescue dog, noticed that Jennie was having trouble getting in and out of the car for trips to the park, she was worried. Then Ashley noticed that her other dog, Pickles, also a 6-year-old shepherd mix, needed help jumping into the car, too.

Ashley scheduled a visit to the vet. When she got there, she got bad news.

"The vet told me that they were so fat they were going to have hip dysplasia in their old age and coronary problems and all kinds of things," Ashley said.

It was a message very similar to one Ashley, a 71-year-old resident of Fort Worth, Texas, heard from her own doctor just days later. Ashley, who was recovering from a minor stroke and whose weight qualifies her as obese, needed to get her cholesterol and blood pressure down, the doctor said.

"I knew we were all in trouble," Ashley said.

Ashley and her pets aren't unique. According to the Centers for Disease Control and Prevention, 34.2 percent of Americans over age 20 were overweight as of 2008, and another 33.8 percent were obese. As human waistlines have ballooned, so has pets' girth: A 2009 national survey of veterinarians by the Association for the Prevention of Pet Obesity found that 45 percent of dogs and 58 percent of cats were overweight or obese. Those numbers revealed a 2 percent increase in dog weight problems from the year before, and a 5 percent increase for cats.

The upsurge in pudgy pets has the same roots as the human obesity epidemic, vets say. Nutritionally unbalanced diets, too many treats and too little exercise all conspire to fatten up Fido. Thanks to these common causes, it's perhaps fitting that new pet weight-loss techniques, from interactive weight-monitoring tools to exercise equipment, are modeled after those meant for their two-legged companions.

Counting canine calories
Someone who stumbled upon the website of the company Nulo could be forgiven for thinking they'd taken a
wrong turn into WeightWatchers . The site is brimming with weight-tracking and meal-planning tools, fitness logs and the promise of "tasty, nutritious food" delivered "to your door." The only difference: Nulo is for pets.

Nulo founder and CEO Michael Landa launched the company in August after noticing an uptick in the requests his Los Angeles-based pet-care business was getting for medically qualified staffers.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

"Over the last four to five years in particular, we've really noticed an increase in our pets that were coming down with things like diabetes, respiratory disease, kidney disease," Landa said. "It really started to put a strain on our pet-sitters."

Just as in humans, extra weight in pets increases the risk for arthritis, joint problems, cardiovascular disease, insulin resistance, diabetes and certain cancers. One 2002 study published in the Journal of the American Veterinary Medical Association found that Labrador retrievers fed restricted-calorie diets had a median life span 2.5 years longer than non-dieting Labradors. The leaner dogs also stayed healthier in their old age.

Landa says he started Nulo to combat a rising trend of low-nutrition pet foods. But the company also strives to combat pet obesity by changing pet owners' behaviors with the interactive tools.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

"What we're trying to do there is get behind the psychology of feeding, much like NutriSystem tries to get behind the psychology of eating," Landa said.

From kibbles to carrots
How much pet owners feed their pets is a major contributor to the pet obesity epidemic, said Ernie Ward, a North Carolina veterinarian and author of "Chow Hounds: Why our Dogs are Getting Fatter — A Vet's Plan to Save Their Lives" (HCI, 2010). The packaging of pet food can be misleading, he said, prompting pet owners to think they're feeding fewer calories than they are. The composition of many pet food brands has also changed to include fewer meats and more corn, soy and wheat, he said.

Ward advocates that people think of their dogs' diets as they do their own: Cut out junk food(in this case, sugary, fatty dog treats) and replace them with whole foods (dogs love to crunch down on raw carrots and broccoli, Ward said).

Pet owners should scan dog food labels and pick brands that list meat as the first ingredient, Ward said. Corn- and wheat-based foods should be avoided, while ingredients like barley and vegetables are a good source of healthy carbohydrates. He also recommends owners consider rotating dog food with low-calorie "real" food, like home-cooked salmon and sweet potatoes. (Some seemingly healthy foods, like grapes and garlic, can be toxic to dogs, so pet owners should consult a vet about what is safe for pets to eat.)

Ward has hope that the pet obesity epidemic won't prove as intractable as the human one, because it's easier to control a dog's response to cravings.

"Dogs don't raid the refrigerator at night," he said. "They don't go to the store and buy junk food."

A walk in the park
If food is half of the weight-loss equation, exercise is the other. Some companies now sell gym-like exercise equipment for dogs, including treadmills and hamster wheels sized for canines.

Of course, a walk in the park is a lot simpler (and probably more dignified for your dog).

Molly Antos, a publicist in Arlington Heights, Ill., adopted a 45-pound (20 kilogram) puggle from relatives. The dog, named Titan, had spent his seven years of life eating everything from pizza to cake, and had already had back surgery related to his obesity. Over three months, Antos and her fiancé coaxed Titan’s weight down to a healthy 27 pounds (12 kg), bribing him with carrots when he didn’t want to walk.

Unfortunately, Titan's story doesn't have a happy ending. Because of extensive nerve and joint damage caused by a lifetime of obesity, Titan had to be euthanized in early September.

That's the kind of fate that Ashley hopes to avoid for Jennie and Pickles. This month, all three have started a training program designed to drop pounds for humans and canines alike.

"I thought, you know, she is not going to enjoy being inside the gym, she's got to walk the dogs anyway, she's very busy professionally and with her family," said Ashley's personal trainer Cindy Hauss, who met her client while they were both volunteering for the Humane Society. "So I just thought, 'Why don't we combine the two?' "

Now, Ashley, Jennie and Pickleswork through two-minute cardio blasts together. Then Ashley drops to the ground for crunches and strength-training while Jennie and Pickles practice obeying "sit" and "stay."